This article presents a new conceptualization of 'shadow curriculum', one component of the worldwide phenomenon of shadow education, i.e. learning outside of school. Traditional conceptions of curriculum are not applicable to shadow education, and so this article begins by exploring how shadow education practices qualify as a new focus of curriculum studies. Based on existing scholarship and our own field experience in South Korea, we propose that shadow curriculum can be defined as supplementary curriculum out of schooling provided by educational business industries that are aimed for individual students' academic success in formal education. The following discussion explores the characteristics of shadow curriculum and shows that incorporating shadow curriculum as a new area of focus in the field of curriculum studies can broaden existing understandings of student learning and the concept of curriculum. Our hope is that this discussion will open a new intellectual space for analysis of the complex phenomenon of shadow education within the field of curriculum studies.